Implantable medical devices (IMDs) are commonly used to provide treatment to patients. Some types of implantable medical devices deliver electrical stimuli to a target tissue via a lead wire (“stimulation lead”) or catheter having one or more electrodes disposed in or about the target tissue. In the context of cardiac rhythm management devices, the electrical stimuli can be delivered in the form of pacing pulses to pace the heart and/or relatively high energy defibrillation shocks or cardioversion shocks to terminate arrhythmias.
The American College of Cardiology/American Heart Association Guidelines for the Evaluation and Management of Chronic Heart Failure in the Adult defines heart failure as a “complex clinical syndrome that can result from any structural or functional cardiac disorder that impairs the ability of the ventricle to fill with or eject blood”. Heart failure has various adverse hemodynamic and circulatory consequences. Signs and symptoms of heart failure include systemic and pulmonary fluid accumulation, reduced activity levels and exercise tolerance, and poor kidney and cerebral/cognitive function, amongst others. Over time, patients with heart failure typically experience further declines in cardiac pump function which is accompanied by increased fluid accumulation, continued decline in activity/exercise tolerance, further decline in kidney and cerebral/cognitive function.
Cardiac resynchronization therapy (CRT) is used to treat the delay in ventricular contractions of the heart that occur in some people with advanced heart failure. A delay between the contraction of the right and left ventricles often occurs with heart failure, leading to biomechanically inefficient heart contractions and reduced cardiac output. Cardiac resynchronization therapy aims to address this problem through stimulation of multiple chambers of the heart in order to resynchronize contraction of the right and left ventricles.
Biomarkers, or biological markers, are substances that can be used as an indicator of a biological state. Biomarkers can include small molecules, proteins, nucleic acids, carbohydrates, lipids, and combinations thereof.